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Ordnance QF 17-pounder
The Ordnance Quick-Firing 17-pounder (or just 17-pdr) was a 76.2 mm (3 inch) gun developed by the United Kingdom during World War II. It was used as an anti-tank gun on its own carriage, as well as equipping a number of British tanks. It was the most effective Allied anti-tank gun of the war. Used with the APDS shot it was capable of defeating all but the thickest armour on German tanks. It was used to 'up-gun' some foreign-built vehicles in British service, notably to produce the Sherman Firefly variant of the US M4 Sherman tank, giving British tank units the ability to hold their own against their German counterparts. In the anti-tank role it was replaced by the 120 mm BAT recoilless rifle after the war. As a tank gun it was succeeded by the 84 mm 20 pounder. __FORCETOC__ History Before the QF 6-pounder had entered service, the British predicted that it would soon be inadequate given the increasing armour of German tanks. In late 1940 design of a replacement was started, and was largely complete by the end of 1941. A prototype production line was set up that spring, and with the appearance of Tiger I tanks in North Africa, the first 100 prototype 17-pounder anti-tank guns were quickly sent off to help counter this new threat. So great was the rush that they were sent before proper carriages had been developed, and the guns had to be mounted in the carriages of 25-pounder gun-howitzers. These early weapons were known as 17/25-pounders and given the codename Pheasant. They first saw action in February 1943. Fully developed 17-pounders started production in 1943 and were first used during the Italian Campaign. The 17-pounder outperformed all other Allied armour-piercing guns, and was quickly adapted for use on various tank chassis. However, few tanks were capable of carrying such a large gun due to the limitation of the size of their turret ring. It was expected that a 75 mm gun under development by Vickers would be used for tanks, but this did not enter service. The British had plans in hand for a tank - based on the Cromwell then under development - to carry the 17-pounder. However the problems inherent in the modifications meant the result, the Cruiser Mark VIII Challenger, was delayed and relatively few built. However, the British devised a conversion for their US-supplied M4 Sherman tanks to take the 17-pounder and it was rushed into service in time for D-Day as the Sherman Firefly. The gun (a modified design was produced specifically for the Firefly) had to be rotated through 90 degrees to fit into the turret of the Sherman, i.e. it lay on its side, and an additional box was welded to the back of the turret to take the radio which was moved to allow for the breech and its recoil. More Shermans were converted until about 50% of Shermans in British service were Fireflies. The British also converted some of their US-produced M10 tank destroyers, replacing the 3-inch (76 mm) gun with the 17-pounder; the resulting vehicles were called 17pdr SP Achilles or just 17-pdr M10. The 17-pounder was also successfully trialled on the Australian-designed Sentinel tank, though no Sentinels equipped with this gun entered service with the Australian Army. The 17-pounder anti-tank guns saw action in Korea, against tanks and in general support use against bunker positions. Afterwards, it was largely replaced in the tank role by the Ordnance QF 20 pounder and in the anti-tank role by the BAT, MOBAT and 120 mm L6 WOMBAT series of recoilless rifles. The United States Army did not use the 17-pounder, though the gun was offered to US forces with a number of Shermans modified for testing. Variants ;Mark I *first production versions. ;Mark II *intended for tank use. Removed the carrier mountings and replaced the muzzle brake with a counterweight. The brake was added back on in March 1944 with the introduction of the APDS shot. The Mk. II was used on the Archer tank destroyer and Challenger tank. ;Mark III *Royal Navy adaptation for use on landing craft, generally similar to the Mk. I, but included an automatic loading system. Unused. ;Mark IV *Another tank adaptation, this time with a different breech where the block slid to the side instead of down to take up less room. Used on Sherman Firefly. ;Mark V *A version of the Mk IV with different mounts to allow it to replace the US 3 in (76.2 mm) Gun M7 on the 3 in SP, Wolverines, creating the 17pdr SP Achilles. ;Mark VI *Another Mk. IV adaptation with a shortened breech. ;Mark VII *Similar to the Mk. VI, yet another change to the breech. ;Straussler Conversion *This was an experimental gun, designed by Nicholas Straussler that was fitted with a motorized gun-carriage. A modified ammunition limber would be attached to the gun's trails, making a four-wheeled, self-propelled vehicle and removing the need for a truck to tow the gun. 77 mm HV The British started work on developing a gun that was small enough to fit on their tank designs - particularly the Cromwell cruiser tank then at the design stage - firing the US 75 mm projectiles (AP shot and HE) but at higher velocity. This gun, a 50 calibre long firing a 75mm projectile attached to a necked down 3-inch (76.2 mm) 20cwt AA gun cartridge through a modified breech, known as the Vickers HV 75 mm, used a larger propellant charge in a larger cartridge. Although the 75 mm HV was a promising weapon, it proved to be too big for the Cromwell tank which was fitted with the normal QF 75 mm gun in use on other British tanks. When the Cromwell's replacement - the Comet - was at the design stage the 75 mm HV concept was reworked to use the 17-pdr ammunition but retaining the 3-inch cartridge firing from a standard 3-inch breech. As the breech length of the 17-pounder was too long to fit in many tanks, a new version was designed with a shorter breech, firing the same projectile as the 17-pounder from a 3-inch 20 cwt AA gun cartridge through a shortened 17-pounder barrel. This new gun's ammunition was not interchangeable with the 17-pounder, so to prevent confusion over ammunition supplies, it was renamed the "77 mm HV"—the 'HV' standing for High Velocity—although it was the same 76.2 mm calibre as the 17-pounder. This gun was used in the Comet tank. Ammunition The 17-pounder used two types of anti-tank ammunition. Armour Piercing, Capped, Ballistic Capped (APCBC) ammunition could penetrate 140 mm of armour at 457 metres and 131 mm at 914 m at a 30-degree angle. Armour-piercing discarding sabot (APDS) could penetrate 208 mm of armour at 457 m and 192 mm at 914 m at a 30-degree angle, allowing it to penetrate the armour of even the German King Tiger heavy tank. However the smaller (sub-calibre) tungsten core of APDS was considered less accurate than APCBC ammunition at ranges beyond 1,000 yards due to rounds which fell short of the target creating much less visible impact. It was thus harder for the gunner to spot the 'fall of shot' and correct his aim. The APDS was also considered to cause less damage to an enemy tank - if it did penetrate the armour - but the sub-calibre tungsten steel core tended to destabilise after penetrating armour and ricochet around inside the armoured target causing crew casualties. APCBC ammunition was standard; APDS shot was used for about 6% of the average load of a 17-pounder equipped British tank. Most sources agree that APDS was not available on D-Day itself but reached Normandy in increasing amounts by the end of June or early July 1944. It was available for the breakout battle from Normandy and the advance to the Netherlands and Germany. The HE shell initially developed for the 17-pounder lacked power. Due to the high-powered cartridge the shell walls had to be thicker to stand the stresses of firing, leaving less room for explosive. Reducing the size of the propelling charge for the HE shell allowed the use of a thinner-walled and more powerful shell. The 17-pounder produced a very large muzzle flash due to the large amount of propellant in its cartridges. Muzzle blast was also significant, described by crews of the anti-tank gun variant as resembling a hard slap on the chest. Use Anti-tank gun The 17-pounder was a much bulkier and heavier weapon than its predecessor. As a result it had to be towed by a gun tractor such as the Morris Quad, M3 Half-track or the Crusader as it could not effectively be moved by its gun crew alone, especially on poor ground. After firing on soft ground the 17-pounder frequently had to be pulled out of the ground due to the gun recoil burying the trail spades. After the Second World War it was issued to anti-tank units of the Royal Artillery in the British Army of the Rhine (BAOR) towed by the M3 Half Track. When the Royal Artillery anti-tank units were disbanded in 1951, transferred to Infantry battalions in the BAOR (6 per battalion), towed by the Oxford Tracked Carrier. It was later replaced by the recoilless 120 mm BAT anti-tank gun. ;25-pounder carriage Stop gap measure named Pheasant. ;Split trail carriage *Split trail carriage, with gunshield. *Weight: 3 t. *Elevation: −6° to +16.5° *Traverse: 60° Israel The Israelis used a number of 17 pounders they captured from the Arabs in the war of independence Category:Weapons